The invention relates to an apparatus for positioning eyepiece of endoscope, and more particularly, to such apparatus which is adapted to permit a picture of an object which has been previously observed to be taken by suitably mounting a photographing device such as camera on an eyepiece assembly.
In an endoscope employing a bundle of optical fibers for transmission of an image and which is used to enable an external observation of the inner wall of a cavity or channel such as a coeliac cavity, the eyepiece assembly of the endoscope includes an eyepiece which is disposed to be movable in the direction of the optical axis to permit an adjustment of the dioptric power of the eyepiece in accordance with the particular condition of the eyes of a viewer. When taking a picture of an image being observed, as by mounting a photographing device such as camera on the eyepiece assembly, the eyepiece is used as part of the objective lens assembly for taking the photograph.
Generally speaking, the position of the eyepiece where a dioptric power adequate for the eyes of a viewer is obtained is different from eyepiece position which should be used when taking a picture. If a good image is formed during the observation process, a sharply focused image cannot be obtained if a picture is taken with the eyepiece maintained in the same position. Consequently, when taking a picture, it is necessary that the eyepiece which has once been adjusted in position to provide an adequate dioptric power for observation purpose be moved to another position. An apparatus for positioning the eyepiece is used at this end. An apparatus is known in which the eyepiece is moved to a given photographing position as a photographing device is mounted on the eyepiece assembly of the endoscope, and a variety of such arrangements have been proposed previously.
By way of example, Japanese Patent Publication No. 44,489/1972 discloses an arrangement including a pin which is driven for sliding movement as a photographing device is mounted on the endoscope so that the eyepiece may be moved to a position where it is free from the influence of a dioptry adjusting cam. Also, Japanese Patent Publication No. 27,677/1970 discloses an arrangement including a cam sleeve which is angularly driven as a photographing device is mounted to move a dioptry adjusting pin to a location where it is free from the influence of a dioptry adjusting cam while permitting a movement of the eyepiece to a photographing position. Finally, Japanese Patent Publication No. 20,263/1977 and Japanese Utility Model Publication No. 23,977/1977 disclose an arrangement including a cam sleeve which is angularly driven as a photographing device is mounted to move a dioptry adjusting pin into cooperation with a photographic positioning cam which is mechanically associated with a dioptry adjusting cam so that an eyepiece integral with the dioptry adjusting pin can be moved to a photographing position.
However, the described arrangements in which the pin or the cam sleeve is either linearly or angularly driven to move the eyepiece beyond the reach of the dioptry adjusting cam are subject to a limitation that a photographing position for the eyepiece cannot be chosen which lies within the extent of the dioptry adjustment.
In the arrangement using the photographic positioning cam which is mechanically associated with the dioptry adjusting cam, the positioning of the eyepiece during a photographing operation is enabled only when the dioptry adjusting pin has moved past the end of the dioptry adjusting cam and bears against the photographing position cam. Hence, it follows that the cam sleeve must be angularly driven through a greater angle than that required for the adjustment of the dioptry in order to move the eyepiece to its photographing position. Thus an angular movement through an increased angle is required as the photographing device is mounted, which makes operation of the photographing device unnecessarily cumbersome.
An endoscope is known which permits a photographing device to be mounted thereon through a mere fitting engagement rather than requiring an angular movement, and is commonly known as an endoscope of the hard type. However, endoscopes of the hard type are generally not provided with a dioptry adjusting mechanism. If some provision is made to permit an adjustment of the dioptry, the positioning of the eyepiece must be performed manually during a photographing operation, again resulting in a cumbersome operation and unreliability.